VOL: 97, ISSUE: 01, PAGE NO: 37
Ann Evans, BSc, RGN, is research nurse, Southmead Hospital, Bristol
Daniel Painter, BSc, MB, BS, is clinical research fellow (urology); andRoger Feneley, MChir, is emeritus consultant urologist, Southmead Hospital, Bristol
Sudden catheter blockage can be distressing for patients and can place extra demands on nursing time and resources (Getliffe, 1990).
Management of a blocked urinary catheter is a common emergency for district nurses and is seen as crisis management because it can occur at any time (Getliffe, 1994a). If there are not enough staff in the community trained to perform male and suprapubic catheterisation, patients need to be referred to A&E departments, placing pressure on the service. About 4% of patients cared for by district nurses have indwelling urinary catheters (Getliffe, 1990). Sassoon et al (1991) demonstrated that 43% of long-term patients experienced problems, and Getliffe (1990) found that over 50% experienced catheter blockage. The problem of catheter encrustation and recurrent blockage has been widely documented (Getliffe, 1991). This article aims to identify reasons for catheter blockage and propose nursing guidelines for their management. There are two distinct groups of reasons why catheters become blocked: - Failure to drain, although the lumen remains patent (mechanical catheter dysfunction); - The lumen actually becoming blocked by an obstructing plug of material, usually encrustation.
Mechanical catheter dysfunction
The word ‘mechanical’ refers to the urine drainage system, the catheter and the urine collection bag, whether body worn or not. It is important to position the bag correctly: it should be well supported and lie below the level of the bladder, to allow urine to drain by gravity (Getliffe, 1996). For example, patients in wheelchairs often use thigh bags. Depending on the patient’s position, these can at times be higher than the bladder, in which case urine drainage ceases. However, the bag should not be more than 30cm lower than the bladder, as the negative pressure created may cause the bladder mucosa to be sucked into the ‘eyes’ of the catheter (Lowthian, 1998). Use an appropriate length of tubing (Getliffe, 1996), as excessive lengths can twist and kink. Constipation can also cause blockage: the overdistended bowel presses on the catheter (McKnight and Rigby, 1995), preventing urine flow.
Long-term catheterisation is when a catheter has been in situ for 28 days or more (Winson, 1997). Indwelling long-term urinary catheters are associated with urinary-tract infection (Mulhall, 1991), as they are an attractive site for bacteria. Bacteria can migrate along the outer surface of the catheter or travel up the internal surface of the drainage tube and catheter. Micro-organisms on the catheter surface form a biofilm, which is a living layer of cells. The cells produce a sticky polysaccharide - glycocalyx - that adheres to the surface of the catheter and protects the bacteria from the effects of antibiotics. A biofilm may start as a small colony of bacteria which rapidly coats the whole catheter surface. Certain types of bacteria, especially those that produce urease - such as Proteus mirabilis - can cause significant problems. The urease causes urea to form ammonia salts, causing urinary pH to rise. Under these alkaline conditions, crystals of struvite (ammonium magnesium phosphate) and hydroxyapatite (calcium phosphate) can form in the urine (Getliffe, 1996). These build up in the catheter lumen, around the eyeholes and around the catheter balloon. The encrustations may fall into the bladder to form bladder stones.
Types of catheter
Catheters should be selected for comfort, and ease of insertion and removal. The ability to minimise complications such as tissue damage and colonisation by micro-organisms should also be considered (Getliffe, 1996). Catheter material for long-term use All-silicone and hydrogel-coated catheters are less likely to encrust than those made of pure latex but no catheter is resistant to encrustation (Morris et al, 1997).
Opinion is divided on the use of all-silicone catheters suprapubically: some manufacturers recommend it, others do not. These catheters take longer to block because they have a wider internal lumen than latex-based coated catheters of the same size. When an all-silicone catheter is removed, the balloon may not return to its original shape. A ‘cuff’ will form around the deflated catheter balloon, resulting in traumatic removal (Evans and Feneley, 2000).
To avoid this, some manufacturers suggest that once the water has been withdrawn from the balloon, the catheter should be left in situ for five minutes - to allow the balloon to regain its original shape - before removal. Rotation of the catheter while slowly withdrawing it may also help. More research is needed to establish whether the ‘cuff’ effect causes problems for nursing staff and discomfort/trauma for patients during catheter removal.
Another problem associated with all-silicone catheters is that the balloon allows some diffusion of water and may occasionally deflate in situ, causing it to fall out (Getliffe, 1996). Urethral catheters It is important to use the smallest diameter of urinary catheter that will allow effective drainage (Woollons, 1996), as larger size catheters - those over 16FG - are associated with abscesses (Roe and Brocklehurst, 1987) and stricture formation in men. Women whose catheter is repeatedly expelled with the balloon should be considered for urgent referral for suprapubic catheterisation. If the problem is allowed to continue, the urethra may suffer irreversible damage and become increasingly patulous, resulting in urine bypassing the lumen and leaking round the catheter. This problem should not be managed by simply increasing the size of catheter or volume of fluid in the balloon.
When choosing a catheter for suprapubic use, the smallest size possible that still provides effective drainage should be used. Suitable sizes are 16-22FG (Winder, 1994) and there appears to be less risk of tissue damage. The problems associated with removing suprapubic catheters are the same as those associated with removing all-silicone catheters.
Bladder-maintenance solutions (instillations and bladder wash-outs) are frequently used to extend catheter life. However, their use remains controversial (Pomfret, 1996). Nurses must be aware of the literature on the use of instillation and possible side-effects. Kennedy et al (1992) suggested that instillations of weak acidic solutions did not effectively reduce catheter encrustation. In this study, a high percentage of red blood cells were noted with Suby G (weak acidic solution) treatment, suggesting that acidic solutions may damage the bladder endothelium. Elliott et al (1989) believe bladder irrigation can lead to an increased shedding of urothelial cells, which play an important role in fighting infection in the bladder. Chlorhexidine has been shown to be ineffective in reducing infections but may be detrimental to the patient in that it can cause haematuria, a burning sensation and irritation to the bladder mucosa (Stickler et al, 1987). Getliffe (1994b), using synthetic urine in a bladder-model system, identified that Suby G and Mandelic acid were effective at reducing encrustation. But there are no conclusive studies to determine the effectiveness of bladder maintenance solutions and a more clinical study is needed. A study on the management of long-term suprapubic catheters (Evans and Feneley, 2000) found that 42% of patients received either a wash-out or instillation. Previous work undertaken by Getliffe (1994a) found that the percentage of patients receiving bladder wash-outs had fallen to 36% from 54% in 1990 (Getliffe, 1990). This implies that nurses continue to rely heavily on the use of bladder maintenance solutions to manage blocked catheters and raises concerns over the potential detrimental effects of these solutions and their cost-effectiveness. Instillations are an expensive way of extending catheter life (Getliffe, 1996). However, no study to date conclusively shows that citric acid bladder instillations prolong catheter life in vivo.
Managing frequently blocking catheters
By monitoring patients with long-term catheters, Getliffe (1996) and Norberg et al (1983) suggested it was possible to establish a ‘characteristic pattern of catheter life’. This can be achieved by keeping a catheter diary, noting the frequency of blockage and the times of catheter changes. It is important to note any visible encrustation on the outside of the catheter and whether bladder-maintenance solutions have been used. Catheters should also be cut open to assess the level of encrustation within the lumen. If catheter life can be predicted in this way, nurses should be able to anticipate when a catheter is likely to block and change it before this happens, thus avoiding crisis catheter management. For example, if a catheter appears to block every three weeks it would be acceptable to change it routinely every two weeks, hopefully avoiding emergency call-outs.
When a patient has a long-term catheter in situ, the responsibility for care falls on the nurse. Ideally the nurse should be trained in urethral and suprapubic catheterisation procedures and should be familiar with the potential complications and how to treat them. Catheter care is not a glamorous subject yet it is essential for patient well-being. Catheter blockage is a common problem which needs to be approached methodically, identifying the cause and taking remedial action to prevent it recurring. Managing blocked catheters is not only a difficult task for nurses, it also increases pressure on emergency services and causes distress to patients and carers. In 1991, Kohler-Ockmore found there was a lack of sound scientific knowledge concerning the use of bladder wash-outs. Getliffe (1996) stated that the evidence surrounding the use of wash-outs remained confusing and conflicting, and Evans and Godfrey (2000) stated that the efficiency of bladder maintenance solutions had yet to be proven. Until the controversy surrounding the use of bladder-maintenance solutions has been resolved, the only method of management left to nurses is to try to pre-empt the blockage of a catheter by changing it before it blocks.